(1) Field of the Invention:
This invention relates to ion-conductive polymers, in other words, to polymeric solid electrolytes and a process for the production thereof.
(2) Description of the Related Art:
Organic polymeric solid electrolytes have been developed in recent years, which compared to inorganic solid electrolytes, have such advantages that (1) they have formability and can be easily formed into thin films of a large area and (2) they have flexibility and hence excellent adhesion with electrodes.
Mixtures of polyethylene oxide and alkali metal salts were proposed as polymeric solid electrolytes by M. B. Armand et al. ["Fast Ion Transport in Solids", 131 (1979)]. The solid electrolytes however had an electrical conductivity as low as 10.sup.-6 S/cm or less at room temperature. Moreover, they exhibited low strength when formed into a thin film, and their adhesion with electrodes was not satisfactory. There has accordingly been a desire for the improvements of these properties.
With a view toward improving their film strength, it has been proposed inter alia to induce crosslinking by the reaction between a trifunctional polyethylene glycol and a diisocyanate derivative (Japanese Patent Laid-Open No. 48716/1987) or by the polymerization reaction of polyethylene glycol diacrylate (Japanese Patent Laid-Open No. 285954/1987). Further improvements have however been desired with respect to the balancing among film strength, ionic conductivity, adhesion with electrodes and so on.